It's a question of how you behave when you're unable to handle the data update. If you need the ability to veto it you have to be an XAResource. If you can simply purge the data form the cache on e.g. lock acquisition failure, then Synchronization is fine provided you are in the same process as the TM. Jonathan. On 04/27/2011 04:55 PM, Mircea Markus wrote: -- Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in UK and Wales under Company Registration No. 3798903 Directors: Michael Cunningham (USA), Charlie Peters (USA), Matt Parsons (USA) and Brendan Lane (Ireland).